Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$120.37	5.572%	$127.077	$127.08	$127.10	$127.10
Purchase #2	$108.25	11.130%	$120.2982	$120.30	$120.30	$120.30
Purchase #3	$160.62	13.478%	$182.2684	$182.27	$182.25	$182.30
Purchase #4	$91.92	6.138%	$97.562	$97.56	$97.55	$97.60
Purchase #5	$98.72	4.645%	$103.3055	$103.31	$103.30	$103.30
Purchase #6	$223.84	11.710%	$250.0517	$250.05	$250.05	$250.10
Purchase #7	$77.40	5.785%	$81.8776	$81.88	$81.90	$81.90
7 purchase totals =	$881.12		$962.4404	$962.45	$962.45	$962.60